The present invention relates generally to safety closures and containers, and more particularly to a one-piece, child-resistant closure and its associated container, the closure including means for effecting a moisture-tight sealing relation between the container and the closure.
Safety closures and containers are in wide use in which the closures have a plurality of locking lugs formed thereon which are cooperative with retaining grooves formed on the container so as to require simultaneous downward and rotational movement of the closure to effect locking engagement of the lugs with the retaining recesses. Such closures are often provided with means therein to bias the locking lugs into locking relation with the retaining recesses on the container with a force sufficient to prevent young children from effecting the proper movement of the closure cap required for removing the closure from the container. See, for example, U.S. Pat. No. 3,344,942 which discloses an annular bell-shaped web which is flexed against the rim of the container to provide the biasing force. The annular web does not flex as readily as desired and provides an uncertain seal. In other closures, the biasing means may also function to attempt to effect a seal with the container. See, e.g., Akers U.S. Pat. No. Re. 30,625. However, the ability of this seal and spring to function satisfactorily after repetitive openings and closings is questionable.
The present invention is particularly directed to medicine vials which are used to package prescription medicine and, consequently, must meet certain standards concerning moisture permeability. Federal standards on moisture vapor permeability require a closure to effect a seal that permits less than 100 milligrams of water vapor per day per liter of volume to enter the sealed container. In order to effect such a seal, it is necessary that the sealing member on the closure be sufficiently pliable to conform to any irregularities in the container surface that the seal engages. However, problems have arisen in one-piece closures where the resilient seal is also used to provide the biasing force. If the seal is sufficiently pliable to provide a moisture tight seal between the closure and container, the seal often does not provide a sufficiently large biasing force to ensure that young children are unable to effect the simultaneous depression and rotation of the cap so to remove it from the container, i.e., the closure is no longer child resistant.
Prior art has addressed the problem of providing a closure cap in which the sealing plug is sufficiently resilient to effect a moisture-tight seal, while ensuring a sufficient biasing force to maintain the closures child-resistant characteristics, by providing two-piece closures, such as those disclosed in U.S. Pat. Nos. 4,053,078 and 4,397,397. The closures shown in these two patents, which have been very successful commercially, employ a separate sealing fitment having a flange overlying the locking lugs on the outer cap and a deep plug that engages the interior cylindrical wall of the vial to form the vapor tight seal. The fitment also provided the spring force to hold the locking lugs within the locking members on the container. Such closures, however, suffer a competitive disadvantage due to the inherently greater expense for manufacturing and assembling two separate pieces, as opposed to a single-piece closure. The two-piece closure requires more molds to be tooled and an additional operation to assemble separate parts.